Glass fabric resin impregnated base coated with a light sensitive layer



United States Patent GLASS FABRIC RESIN IMPREGNATED BASE COATED WITH ALIGHT SENSITIVE LAYER Adrian Eichorn, Topanga, Calif., assignor toScreen Engineering C0., Santa Monica, Calif., a corporation ofCalifornia No Drawing. Application February 19, 1953 Serial No. 337,890

7 Claims. (CI. 96-75) This application is a continuation in part of mycopending application Serial No. 787,855, filed November 24, 1947, nowabandoned.

It has long been a vexing problem, particularly in aircraftconstruction, to find some way to counteract or neutralize thedimensional instability of conventional drawing surfaces such as paper,tracing cloth, and the like, employed in making full scale drawings forprototypes or patterns, since such materials are hygroscopic and expandor contract with changes of atmospheric moisture (as well as withtemperature changes), thus throwing ofi the minute tolerances and exactdimensions necessary for precision machining.

Due to this particular difiicnlty, countless hours have been expended inslowly scribing production drawings on metal templates, such as sheetaluminum. In the alternative, many attempts have been made, either todraw on some other more stable material, or to directly attach a lessstable sheet of paper, or the like, to the metal template. Thus,drawings have been made on metalfoil, or paper drawings made to scalehave been attached to metal or other backing by use of various plasticor adhesive compositions. Numerous attempts have also been made totransfer such drawings to templates by means of photo-sensitivematerials, but these have generally relied on a reflex transfer of thedrawing to the metal from the hygroscopic drawing sheet attached by onemeans or another to a more stable support.

By the present invention, however, there is provided a photosensitivelight-transmitting, flexible sheet, dimen: sionally stable against bothheat and humidity changes, upon which sheet, original, full-scaleproduction drawings can be photographically copied from a drawingprovided on dimensionally stable material and which sheet can beemployed to produce any number of clear and precise, either right orleft-hand prints directlyupon a template, metal workpiece or othermaterial.

The present process is based upon the combination.

or association of a light-transmitting, dimensionally stable sheet ofbacking material, with a coating substance,

also transparent or translucent, which coating, after appli-.

surface being printed upon, a much greater thickness of glass cloth maybe employed, as long as it will transmit light.

The glass cloth is made up of a woven glass fabric impregnated with astiffening substance of polyester or allyl resin in order to impart thedesired rigidity to ice the fabric. Such resin, eifectively contributesto the physical properties of the fabric. By filing the intersticesbetween the glass fibers, it overcomes the tendency of the individualfibers to scatter or diffuse light without reducing the lighttransmission. It also contributes to the thermal and hygroscopicstability of the finished sheet. The polyester resins suitable for thispurpose are the polymerization product of a mixture of a compound havinga single terminal ethylenic group CH =C with an unsaturated alkyd resinwhich is the reaction product of an ethylenic-alpha-beta dicarboxylicacid with a glycol. These ingredients are reacted in such proportionsthat there are present in the reacting mixture about one carboxyl groupin such unsaturated acid to one hydroxyl group in such glycol to anadvanced stage of esterification, but short of becoming completelyinsoluble and infusible, until a product of low acid number is producedwhich is soluble in a liquid monomeric unsaturated polymerizablecompound containing an ethylenic linkage. This product of esterificationis mixed with a liquid monomeric unsaturated polymerizable compoundcontaining an ethylenic linkage. The glass fabric is impregnated withthis solution and the solution is subjected to conjoint polymerizationin the absence of air to form an insoluble, infusible resin filling theinterstices of the glass fabric.

Probably the best commercial example of these resins is the resin formedfrom a mixture of styrene with diethylene glycol maleate. However,compounds other than styrene which have a single terminal ethylenicgroup may be used; e. g. alpha substituted ethylene compounds of thegeneral formula CH =CR R where R is a negative group such as aryl,vinyl, ethynyl, carboxyl, halogeno, O-CO-alkyl (acyloxy), C0.0 alkyl(carbalkoxy), alkoxy, aldehyde, nitrilo or halovinyl, and R is hydrogenor an alkyl group.

These compounds are in contrast with the unsaturated polybasic acidsused to form the polyester resins which acids may be defined as ethylenealpha-beta dicarboxylic acids. In addition to maleic acid or anhydride,fumaric acid, itaconic acid and citraconic acids and anhydrides may beused. The dihydric alcohol or glycol may be diethylene glycol, ethyleneglycol, triethylene glycol, trimethylene glycol, monoethylin, orpropylene glycol and its derivatives. The dicarboxylic acids anddihydric alcohols form chain compounds which may be termed linearpolyesters. In the final cure the linear molecule is converted by thesubstituted-ethylene body with which it is mixed to a molecule of the3-dimensional type (insoluble and infusible) by some form ofcross-linkage between the linear molecules. The cross-linkage causingcure is believed to be a copolymerization between the unsaturated alkydresin and the monomeric resin forming body.

Plasticizers may be added to the stiffening resin to make thedimensionally stable sheet more flexible and less brittle. For example,the phthalate of diethylene glycol monoethyl ether, sucrose octacetate,camphor, diethyleneglycol phthalate, glycol succinate, diethylene glycoloxalate and glycol benzoate-phthalate.

The stifiening resin filler is generally incorporated in the glass clothby passing a strip of the latter through a tank of the designated resin,then drawing it between squeezing rollers and heating the fabric on theorder of 15-20 minutes at about 200 F.

By the present process, the resin-impregnated sheet is coated with anadhesive layer of organic plastic material on an intimate mixture ofthree resinous or plastic ingredients. These are (1) an air-drying,film-forming plastic, such as nitrated cellulose of the type commonlyused in lacquer, (2) a plasticizing and adhesive substance, such asalkyd resin which solidifies or polymerizes upon subsequent baking ofthe coated sheet, and (3) melamine (aldehyde resin) which is polymerizedin situ to contribute hai'dness to the solidified coating.

The lacquer grade of cellulose nitrate which is conveniently employedcontains about 11% nitrogen. However, this amount is not critical forthe present purpose and other grades of nitrated cellulose havinggreater or lesser amount of nitrogen may likewise be used. If desired,amounts of other plasticizer may also be present, such as high-boilingesters as cresyl or phenyl phosphates and phthalates; likewisechlorinated hydrocarbons, caster oil and/or camphor; again polyesterresins may be used for this purpose audit is conceivable thatthepresence of the impregnated polyester resin in the glass fibre sheetpromotes the adhesion thereto of the coat of cellulose nitrateplasticized with polyester resin. Polyester resins having air-dryingproperties may also promote the solidification 'or hardening of thefilm. Amounts of plasticizer on the order of about 1% to 5% by weight,are applicable although, again, this range is not critical. It is betterto avoid use of volatile plasticizers, as they might slightly effect thestability of the sheet over a period of time.

Alkyd resinsfas is well known, are the esterification products ofpolyacids suchas phthalate, maleic, succinic, etc., with polyhydroxyalcohols, and in particular, the reaction product of glycol or glycerolwith ph'thalic anhydride. Desirably, the commercial, oil-modified alkydresin, such as is employed in varnishes and lacquers, is used. Itcontains added amounts of air-drying ingredients, such as drying oil (e.g., triglycerides of unsaturated mono acids such as linoleic). However,non-air-drying alkyd resin is also applicable.

It will be realized, of course, that alkyd resin, as well as themelamine resin, are not generally air-drying, but are polymerized byheat. Accordingly, it is seen that in the present combination, thenitrated cellulose acts as a spreading agent for the other ingredients,promoting adhesion of the mixture to the glass cloth and forming anair-drying film of the sameafter spreading, while the other resinouscomponents are later hardened or polymerized, chiefly by subsequentheating, although over a period of time they would tend to harden byexposure to air without heat.

In the resinous component, I may use, for example, 45 parts cellulosenitrate, 45 parts melamine, and parts alkyd resin (by weight), althoughsuch proportions can be varied widely, a workable range beingapproximately:

Example I Cellulose nitrate 30-50 Melamine 30-50 Oil modified alkydresin 5-20 In this embodiment, the melamine aldehyde resin contributes anecessary hardness to the solidified coating and in contrast to theoil-modified alkyd resin which may harden in time in the presence ofoxygen, melamine resin generally requires a catalyst and/or baking tosolidify. Accordingly, the alkyd resin may be regarded in this respectin part as a binder for the nitrocellulose and melamine.

In addition to the mixed resinous component of the coating composition,there is desirably present a slightly abrasive material which will givea tooth to the coating so as to receive the graphite markings from thedrawing pencil. For the tooth material I prefer siliceous materials suchas a mixture of talc with colloidal silica or diatomaceous earth. Thus,I may use, for example, 100 parts silica, with 100 parts of theforegoing resinous mixture. These proportions are not, however,critical. For use with a lighter drawing pencil, the tooth materialcould be reduced, say, by half.

With approximately 40 parts (by volume) of the foregoing intimatemixture of resin and abrasive agent there is also incorporated an amount(e. g., 40 to parts) of solvent or dispersing agent capable of providinga fluid mass and of preventing the separation of the several ingredientsupon standing. Desirably, such an inert liquid vehicle possesses a lowvapor pressure so as to minimize loss by evaporation, and for thispurpose I prefer an organic compound containing both a hydroxyl radicaland an ether linkage such as the lower alkyl ethers of ethylene glycol,propylene glycol, diethylene glycol, etc. Particular mention may be madeof the dior poly-hydroxy compounds, such as the lower monoallcyl ethersof diethylene glycol. Such glycol ethers generally contain from one tofour or six (or more) carbon atoms in each, usually alkyl, carbon chainwithin the molecule, 6. g., methyl, ethyl, butyl, phenyl, etc. Otherapplicable solvents which may be used in Whole or part include: esterssuch as methyl-, ethyl-, amyl-, butyl-acetates, lactates, etc.; thecorresponding alcohols and ketones, diacetone alcohol, etc.

Such a composition may be stored indefinitely. Before the coating isapplied, it is first diluted with a thinner, of which a typical formulais:

parts of the solvent used above, e. g., mono butyl etherof diethyleneglycol.

10 parts aromatic hydrocarbon mixture, such as commercial toluol.

2 parts adhesive ingredient, such as styrene.

% part polymerization catalyst for melamine, such as phosphoric acid.

The amount of thinner employed varies with the particular method bywhich the coating is to be applied to the glass cloth. For coating withsilk screen process, for example, about volume of thinner is used. Ifthe composition is to be applied by brushing or roller coating, a lessviscous solution is desired. After application, the coated sheet isheated, on the order of SOminutes at 240 F., to solidify the coating.

A wide variety of other coatings may be applied to the filled glassfabric base sheet in order to provide an adherent overcoat of a filmforming organic material containing an abrasive agent to impart penciltake to the dimensionally stable drawing material. For example,transparent coatings containing one or more of the following resins incombination with suitable plasticizers and an abrasive agent may beused; e. g. nitro cellulose, other cellulose esters such as, celluloseacetate, alkyd resins, vinyl resin, various vinyl copolymers, ureaformaldehyde and melamine formaldehyde. The following specific ex amplesillustrate coating compositions which may be appliedby kiss coating froma roller. By varying the solvent proportions, suitable compositionsforspraying or screen application may be obtained. In the followingformulae all resin proportions are on a solid weight basis.

AIR DRY TYPES Example ll NITROCELLULOSE Parts Nitrocellulose RS (60-80seconds) Modified rosin, such as Teglac 2-152 (American Cyanamide) 50Dioctyl phthalate plasticizer 2O Diatomaceous earth 6O Toluol 450Ethanol 80 Ethyl acetate 425 Butyl acetate -z 5 0 Example IIINITROCELLULOSE-ALKYD Parts Nitrocellulose RS (60-80 seconds) 100 Highphthalic oxidizing alkyd, such as Rezyl 387-5 (American Cyanamide) 220Diatomaceous earth 110 Toluol 550 Ethanol 75 Butanol 75 Ethyl acetate350 Butyl acetate 90 Example IV VINYL Parts Vinyl chloride-acetatecopolymer, such as Vinylite VAGH (Carbide & Carbon) l Diatomaceous earth35 Toluol 25 Methyl ethyl ketone 65 Methyl isobutyl ketone 35 IsophoroneAs previously noted, glass cloth coated with the foregoing, translucent,resin mixtures containing an abrasive agent can be drawn upon withpencil or ink and the opaque pencil lines pattern the light transmittedthrough the sheet onto any light-sensitive material. The drawing couldsimilarly be made with ink. In the alternative, a highly pigmentedcoating including a white pigment such as titanium dioxide or a darkpigment (such as practically any color, paint pigment as chromiumhydrate or toluidine red) may be employed to produce an opaque coatingwhich may be scratched by a dry pen or metal scribe so that in makingprints from such a drawing light passes only through the scribed lines.In addition to titanium dioxide other white pigments such as zinc orlead oxide or sulphide may be substituted in whole or in part.

Since the present drawings are both light-transmitting and dimensionallystable, they may be used to transfer or reproduce the drawings directlyonto a template, prototype or other surface. Such a surface may then bedrilled, cut or otherwise shaped. Thus it may form the actual wing of anairplane, for example, being cut and drilled along the transferreddrawing lines.

For this purpose, there are also provided fluid compositions containinglight-sensitive ingredients which may be applied to metal surfaces andcaused thereupon to solidify. After exposure to light transmittedthrough one of the above drawings, the metal coating can then be readilydeveloped simply by flooding with water or by other appropriate means.

Conventional blueprint salts (e. g., ferric ammonium citrate andpotassium ferricyanide) may be thus applied in a carrier such asaqueous, hydrolyzed cellulose (e. g. hydroxy ethyl cellulose, sodiumcarboxymethylcellulose, etc.) containing a tanning or hardening agentsuch as a lower molecular weight aldehyde (formaldehyde, glyoxalparaldehyde, etc.) which renders the carrier hard or water-insolubleafter application to the metal. An aldehyde concentration of about 15%to 35% of the hydrolyzed cellulose is generally applicable. Suchhardening action is apparently promoted by a mildly acid solution on theorder of about pH 6.5 to about pH 4.5, although the solution need not beacidic. The function of the carrier is, of course, to evenly distributeand fasten the light-sensitive salts to the metal surface. The action ofthe aldehyde on the hydrolyzed cellulose is only apparent after theaqueous film of the latter has lostmost of its water content; in otherwords, as long as the cellulose is kept wet it does not harden.

Other coagulable carbohydrate or proteinaceous substances may besubstituted in whole or part for the hydrated cellulose, including gumacacia, gum tragacanth,

Parts by weight Hydroxy ethylcellulose 12 Glyoxal (dialdehyde) 4 Flowagent 50 (Ethylene glycol monobutyl ether 49) (Ethyl lactate 49) (Octylalcohol 2) Distilled water 500 Ferric ammonium citrate (green scales) 50Citric acid 30 Potassium ferricyanide 11 Hydroxy ethylcellulose 12Formaldehyde 2 Flow agent 50 (Ethylene glycol monobutyl ether 49) (Ethyllactate 49) (Trimethyl cyclohexanol 2) Distilled water 500 Ferricammonium citrate (green scales) 50 Citric acid 30 Potassium ferricyanide11 III Hydroxyethylcellulose 12 Glyoxal (dialdehyde) 4 Flow agent(either of above) 20 Distilled water 200 Ferric ammonium citrate (greenscales) 15 Ferric ammonium oxalate 15 Ferric oxalate 2 Potassiumferricyanide 5 IV Sodium carboxymethylcellulose 6 Dialdehyde 2 Flowagent (either of above) 20 Distilled water 200 Ferric ammonium citrate(green scales) 6 Ferric ammonium oxalate 18 Ferric chloride 2 Potassiumcitrate 2 Potassium ferricyanide 4 starch gums, dextrin, gelatin,albumins, histories, etc.

They may be hardened by application of heat and/or hardening agents,such as ammonium sulfate, chromium aluminum sulfate, solublebichromates, etc.

The amount of hydrolyzed cellulose or other coagulable ingredient usedwill depend upon the viscosity permitted by the particular method ofapplication. For silk screen process, a viscosity of about 250 to 1000centipoises is applicable; for brush and roller coating, about to 250centipoises; for spraying, about 35 to 75 centipoises.

There may also be present about 0.5% to 10% of a surface active orwetting agent, such as those listed in Industrial and EngineeringChemistry, vol. 35, pages 126130 (January 1943); also about 5% to 20% ofa flow agent, such as the hydroxy ethers listed earlier; andparticularly for silk screen application, there may be included about0.1% to 0.5 of a defoaming agent, such as cyclohexanol, octyl alcohol,etc.

Several suitable formulas are as follows:

Variations of the blueprint salts to 10% have little effect on qualityor speed of print. Increase of potassium ferricyanide slows up theprinting time. Decrease of ferric ammonium citrate decreases quality orbrilliance of print. Decided decrease of citric acid tends to make aweaker, or softer film. Apparently the pH or acidity of the solutioncombined with the aldehyde determines the hardness or strength of thefilm. Increase of citric acid lowers the keeping quality of thesolution.

Generally the metal is first covered with conventional white templatepaint in, order to improve the contrast of the print and prevent theblueprint salts from coming into contact with the base metal which wouldslowly decompose the light-sensitive salts and reduce theireffectiveness. However, it may be etched or anodized and thelight-sensitive coating then applied direct. The hydrolyzed cellulosecoating hardens in about one-half to two hours, and the drawing is thenplaced over it and exposed to light such as photo flood light, arelight, mercury vapor, sunlight, etc. Following exposure, the metalsurface is swabbed with Water containing about 2% potassium bichromateaccording toconventional blueprint procedure, and then washed with coldwater. Upon drying, the drawing will be found to have been printed uponthe metal with great clarity and precision. If the. drawing has beenmade with pencil, or ink upon. the glass cloth containing a translucentcoating, they will show onthe metal as white lines on a blue background.If the original drawing was made with a scribe upon an opaque coating,the metal print will have blue lines on a white background. In eitherevent, a right or left-hand print will be made (without a negative)depending upon whether the inscribed face or the reverse face of thedrawing is placed next to the metal.

In place of the blueprint salts brownprint or Van Dyke salts may be usedor diazo-type dye forming components (such as described in the BritishPatents Nos. 210,862 and 234,818 and in German Patents Nos. 376,385 and386,433) and the print developed with aqueous ammonia vapor or by thesemi-wet method. Bichromated gelatin coatings or gelatin coatingscontaining silver halides may also be applied to the metal for thispurpose.

In the particular method of the present invention, the drawing may beused to produce a duplicate drawing upon a sheet of glass cloth coatedwith suitable light-sensitive salts. Such duplicate drawing can then, ofcourse, be used to make line prints upon any suitable material. Twodifferent formulae for coating the glass cloth to form a Van Dykenegative are:

Hydroxy ethylcellulose 12 Dialdehyde 4 Flow agent (as above) 2O Ferricammonium citrate (green scales) 17.5 Silver nitrate 5 Citric acid l0Distilled water 200 Sodium carboxymethylcellulose 6 Formaldehyde 2 Flowagent 20 Ferric ammonium oxalate 20 Silver nitrate 7 Distilled water 200Gelatin may also be used as a carrier in these as Well as the earlierformulae. This would require heating of the solution before application.

The coated glass clothsheet is contacted to the drawing or the otherglass cloth sheet, in a printing frame, then exposed to light. The printis washed in water, then fixed in a 2% hypo bath, then again washed inwater.

Other types of photosensitive coatings may be applied to the glass clothbase sheet which is filled with a polyester resin. For example,conventional silver halide emulsions for contact, reflex or projectionprinting may be employed anddiazotype coatings of both the dry andmoist'developingtypes may also be used on the glass cloth base materialas well as dichromated colloid coatings. As is well understood in thediazotype art, the so-called dry developing diazotype layers contain alight-sensitive diazo compound and an azo dye coupling component whichwill couple with the diazo compound in the presence of ammonia fumes.The so-called moist developing diazotype layers contain only thelight-sensitive diazo compound, the azo coupling component beingcontained in analkaline moistening solution used for developing theimage. In each case, the light-sensitive substances are applied insolution with other common ingredients as is customary in the art andwhere required subcoatings may be applied in order to make the basereceptive tothe light-sensitive coatings in accord with conventionalpractice in. the art of photosensitive coating. The photosensitivecoating may be applied over a coating containing an abra ed: agentsimilar to-the various coatings previously described for this purpose ifit is desired that corrections or revisions of the drawing may be madeon the sheet provided with the photographically formed image.

While I have described the present compositions and processes byreference to particular materials and exact proportions, it is to beunderstood that these are given by way of illustration rather than asnecessary limitations of the invention which is to be broadly construedas hereafter defined, having in mind such modifications and substitutionof equivalents as will occur to those skilled in the art.

Having thus described the invention what is claimed l. A dimensionallystable light transmitting photosensitive flexibie sheet material forcopying a highly precise image which may be recopied comprising a wovenglass fabric filled with a polyester resin which is the polymerizationproduct of styrene and the reaction product of a dicarboxylic acidselected from the group consisting of maleic, fumaric, itaconic andcitraconic acids with a dihydric alcohol selected from the groupconsisting of ethylene glycol, diethylene glycol, triethylene glycol,trimethylene glycol, monoethylin and propylene glycol and an adherentovercoat of a silver halide photographic emulsion on the surface of thefilled fabric.

2. A dimensionally stable light transmitting photosensitive flexiblesheet material for copying a highly precise image which may be recopiedcomprising a woven glass fabric filled with a polyester resin which isthe polymerization product of styrene and the reaction product of adicarboxylic acid selected from the group consisting of maleic, fumaric,itaconic and citraconic acids with a dihydric alcohol selected from thegroup consisting of ethylene glycol, diethylene glycol, triethyleneglycol, trimethylene glycol, monoethylin and propylene glycol and anadherent overcoat of a film forming organic material carrying a lightsensitive ferric salt on the surface of the filled fabric.

3. A dimensionally stable lig.t transmitting photosensitive flexiblesheet material for copying a highly precise image which may be recopiedcomprising a woven glass fabric filled with a polyester resin which isthe polymerization product of styrene and the reaction product of adicarboxylic acid selected from the group consisting of maleic, fumaric,itaconic and citraconic acids with a dihydric alcohol selected from thegroup consisting of ethylene glycol, diethylene glycol, triethyleneglycol, trimethylene glycol, monoethylin and propylene glycol and anadherent overcoat of a film forming organic material carrying a lightsensitive ferric salt and a water soluble silver salt on the surface ofthe filled fabric.

4. A dimensionally stable light transmitting photosensitive flexiblesheet material for copying a highly precise image which may be recopiedcomprising a woven glass fabric filled with a polyester resin which isthe polymerization product of styrene and the reaction product of adicarboxyiic acid selected from the group consisting of maleic, fumaric,itaconic and citraconic acids with a dihydric alcohol selected from thegroup consisting of ethylene glycol, diethylene glycol, triethyleneglycol, trimethylene glycol, monoethylin and propylene glycol and anadherent overcoat of a film forming orgauic material carrying a lightsensitive diazo compound on the surface of the filled fabric.

5. A dimensionally stable light transmitting photosensitive flexiblesheet material for copying a highly precise image which may be recopiedcomprising a woven glass fabric filled with a polyester resin which isthe polymerization product of styrene and the reaction product of adicarboxylic acid selected from the group consisting of maleic, fumaric,itaconic and citraconic acids with a dihydric alcohol selected from thegroup consisting of ethylene glycol, diethylene glycol, triethyleneglycol, trimethylene glycol, monoethylin and propylene glycol and anadherent overcoat of a film forming organic material carrying a lightsensitive diazo compound and an azo dye coupling component on thesurface of the filled fabric.

6. A dimensionally stable light transmitting photosensitive flexiblesheet material for copying a highly precise image which may be recopiedcomprising a woven glass fabric filled with a polyester resin which isthe polymerization product of styrene with the reaction product of adicarboxylic acid selected from the group consisting of maleic, fumaric,itaconic and citraconic acids and a dihydric alcohol selected from thegroup consisting of ethylene glycol, diethylene glycol, triethyl- 25 eneglycol, trimethylene glycol, monoethylin, propylene glycol and anadherent overcoat of a film forming organic material carrying aphotosensitive substance selected from the group consisting of ferricsalts, diazo 10 compounds, silver halides and bichromated colloids onthe surface of the filled fabric.

7. A dimensionally stable light transmitting photosensitive flexiblesheet material for copying a highly precise image which may be recopiedcomprising a Woven glass fabric filled wth a polyester resin which isthe polymerization product of styrene with diethylene glycol maleate andan adherent overcoat of a film forming organic material carrying aphotosensitive substance selected from the group consisting of ferricsalts, diazo compounds, silver halides and bichromated colloids on thesurface of the filled fabric.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES British Plastics, June 1950, pages 272-280. in Scien. L.)

Industrial and Engineering Chemistry, February 1950, pages 114 to 119.(Copy in Scientific Library.)

6. A DIMENSIONALLY STABLE LIGHT TRANSMITTING PHOTOSENSATIVE FLEXIBLESHEET MATERIAL FOR COPYING A HIGHLY PRECISE IMAGE WHICH MAY BE RECOPIEDCOMPRISING A WOVEN GLASS FABRIC FILLED WITH A POLYESTER RESIN WHICH ISTHE POLYMERIZATION PRODUCT OF STYRENE WITH THE REACTION PRODUCT OF ADICARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF MALEIC, FUMARIC,ITACONIC AND CITRACONIC ACIDS AND A DIHYDRIC ALCOHOL SELECTED FROM THEGROUP CONSISTING OF ETHYLENE GLYCOL, DIETHYLENE GLYCOL, TRIETHYLENEGLYCOL, TRIMETHYLENE GLYCOL, MONOETHYLIN, PROPYLENE GLYCOL AND ANADHERENT OVERCOAT OF A FILM FORMING ORGANIC MATERIAL CARRYING APHOTOSENSITIVE SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF FERRICSALTS, DIAZO COMPOUNDS, SILVER HALIDES AND BICHROMATED COLLOIDS ON THESURFACE OF THE FILLED FABRIC.